An artist’s rendering shows plans for an expanded San Diego Convention Center that include a 5-acre park on the roof.

The two men running for San Diego mayor rarely see eye-to-eye on anything, but Republican City Councilman Carl DeMaio and Democratic Rep. Bob Filner do agree on one thing: If you want to know how they’ll govern as mayor, look at the stance they took earlier this year on the proposed convention center expansion.

DeMaio has adamantly opposed tax increases yet voted in favor of the expansion’s financing plan, which calls for hotel surcharges to cover a bulk of the $520 million cost. He called it a thoughtful and balanced solution to aid the local economy that is largely paid for by hotels. DeMaio accused Filner of using the issue as a political football during a campaign by siding with unions in opposition.

Filner, who supports an expansion, adamantly opposed the plan and called it “the most blatant giveaway” of taxpayer money he’s ever seen. He said a public tax should be put to a public vote and accused city leaders of allowing a small but powerful group — hoteliers — too much say over a major economic engine. Filner accused DeMaio of kowtowing to the special interests that back his campaign by voting for the proposal.

The differing opinions on the project will likely have ramifications beyond the campaign trail. The expansion is anything but certain, as only the financing plan has won approval by the City Council and has yet to be validated in court. In other words, current Mayor Jerry Sanders got the ball rolling, but the next mayor will need to shepherd the project through the California Coastal Commission as labor and environmentalists voice their misgivings.

DeMaio says his opponent’s outspoken opposition to the proposal shows he’s not ready to assume leadership of the nation’s eighth largest city.

“You have one mayoral candidate who is trying to divide and derail an important project for political gain,” he said. “When you have a project like this that could put San Diegans back to work, that will bring millions of dollars in for municipal services, it’s a shame that some folks would seek to divide and derail rather than unite and move our city forward.”

Filner, who last month said he would support the plan as mayor if a court deems it legal, said the City Council approval of the financing plan is exactly why the city needs someone like him as the next mayor.

“They thought nothing of giving one private group … the authority to control all this money,” Filner said. “That’s got to change. That’s what I represent. Who’s going to be looking out for the public in all this? It’s been a small group of people that control these decisions. … I watched this stuff in utter disbelief. Usually they’re more subtle about giving away public money. This was so blatant. That’s going to be the biggest change here when I’m mayor.”

The proposed $520 million expansion calls for about 220,150 square feet of additional exhibit hall space for a combined total of 745,850 square feet, as well as 101,500 more square feet of meeting rooms and 78,470 square feet of ballroom space. The extra space is needed, supporters say, to retain major events such as Comic-Con and compete with other cities for coveted trade shows, all of which boost the local economy.